Low back pain and pelvic girdle pain affects more than half of all pregnant women, making it difficult for them to cope with, and participate in everyday activities. - Leto Belt can help. While there can be several factors that can contribute to back and pelvic pain in pregnancy, the most common cause is the increased laxity of the joints of the pelvis (sacroiliac and/or pubic symphysis). The loss of core muscle support from the expanding abdomen and the change centre of gravity can also contribute.